Hands too large...
Join Date: Feb 2009
Location: South Africa
County: Northern Cape
I once had a similar knocking noise on a 2.0 T/spark that was caused by a balancing shaft belt, having jumped a tooth or two on one of the pulleys. This was identified by manually revving the engine, with the cam-belt covers removed, and observing the balancing belt tensioner. There was an observable jerk on the tensioner, coinciding with every knocking sound, which indicated that the front balancing shaft was hitting the crank-shaft/con-rods somewhere.
After removing the balancing belt, an oil and filter change was also required, in order to get rid of the metal grit in the oil caused by the knocking wear and tear.
Personally I am of the opinion that the additional comfort from using a balancing belt is not worth the additional risk of catastrophic failure associated with the belt.